Hi, first time poster and long time lurker here. Great topic!
For recreating “analogue” sounding sounds I was mostly trying to emulate the behaviour of classic analogue (poly) synth on the digitone, which is perfectly possibe in my opinion. But it is a bit of a lengthy process to explain.
- The first step is to recreate classic waveforms in the oscillator section (e.g. saw and square). For classic poly synth sounds I experimented with algorithm 2 (two independent towers of carrier and modulator) to create a simple dual oscillator setup.
Step a.) Getting the waveforms right is the most important step. But do not worry If they do not look right on an oscilloscope, use your ears. For a sawtooth like sound I use a 1:1 ratio between carrier and modulator in one of the towers and increase the modulation index (LEVEL on the first SYN2 page) until I like what I hear. For a pulse-like sound I use a ratio of 1:2 and increase the modulation index until I like what I hear. The levels of the osciallators can be mixed freely on the first SYN1 page, for instance with an LFO. Nice! If I want to detune the two oscillator stacks, I simply use the first and second SYN1 pages. For instance, if I want to make the first tower a squarish sub oscillator playing one octave below, I simply change C to 0.5 and A to 1 on the first SYN1 page. If I want other intervals between the two oscillator stacks, I use the second SYN1 page (detuning C and A by the same amount).
- The rest is simply just sound design as one would do on a standard analog synth as filters and amplitude envelopes as well as LFOs and the sequencer (!) are readily available. Some ideas:
a.) Feedback on a modulator carrier stack really helps with getting more defined saw like sounds. So if I want a strongly defined saw, I mostly use tower 2 in Algo 2 with a ratio of 1:1 and adjust the feedback on modulator B.
b.) Slightly detuning the oscillators (there are various possbilities on the digitone for doing that) allows for getting a bit more lively, scintillating spectrum with a pleasent phasing effect, just experiment. Personally, I like to use the fine tuning on the second SYN2 page for that purpose.
c.) For creating classic “analogue” sounds, I do not use the envelopes for the modulation index (first SYN2 page), because they do not appear on classic analogue synths. However, they are great for modeling the energy trajectory of the frequency modulation.
d.) Personally, I find that effects like reverb are more like a last resort to add a bit of polish. The main goal is to create a good sound in the first place, but well, I love a good sounding reverb. 
e.) If you are using a velocity and aftertouch sensitive controller, pay attention on how the sound feels when playing it. The setup page has some great options for fine tuning how the synth engines react to frequency, velocity and aftertouch, that is, ultimately, your physical interactions with the synth engines. Unfortunately, polyphonic aftertouch is not available.
That’s basically it: Create a classic sounding oscillator section and work from there with the filter, envelopes and modulation options. Add internal or external effects to taste.
To wrap this up: the digitone is capable of producing a huge variety of sounds. Just experiment until you find something that sounds good to your ears!
By the way, if someone has a recipe for the classic FM soprano patch or formant synthesis on the digitione, let me know!
Hope that helps! Best wishes!
Really great to hear that people get use out of the tutorial